Apparatus and method for the manufacture of uniform impedance communications cables for high frequency use

ABSTRACT

Machine for manufacturing uniform impedance communication cables for high frequency use includes a series of staggered double twisting units or heads each of which supports two reels wound with single wire elements or conductors, and a constant tension tape dispenser. The wire elements from the reels as well as the tape from the tape dispenser are simultaneously unwound and guided to the ends of the rotating bows of the twisting units at which points the individual wire elements or conductors are twisted about each other and the tape is applied to the twisted wire pair to fix and maintain the spatial integrity of the twisted wires relative to each other. Each twisting unit rotated at slightly different speeds to assure different lay lengths for each twisted pair. The twisted pairs are guided downstream by a capstan and all of the twisted and taped wire sets are secured to each other by a pre-twisting and taping operation before the composite cable is wound onto a rotating take-up unit. A number of different design modifications are described for producing both simple and complex cable constructions which include twisted pairs, triads and quads.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-art of application Ser. No.08/225,852 filed on Apr. 8, 1994.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention generally relates to an apparatus and method for themanufacture of high quality communication cables of the type including asingle or a plurality of sets of twisted wires.

2. Description of the Prior Art

Communication cables of the type which include a plurality of twistedwires are manufactured in either one stage or in two stages.

In the case where cables are manufactured in two stages, the twistedwires are firstly prepared by twisting the wires together by means ofso-called twinning or pairing machines. Twisted wires are then made upinto communication cables by means of, for example, stationary take-ups,rotating take-ups (also called drum twisting machines) or other type ofrotating equipment.

One form of equipment conventionally used for twisting 2, 3 or 4 wiresis the double twist machines. The resulting twisted elements are calledpairs, triads or quads.

This equipment includes a bobbin cradle around which is arranged arotatable frame or bow which is driven to turn around the cradle. Wiresto be twisted may be supplied from bobbins on the bobbin cradle insidethe twisting cage and taken up on a take-up reel outside the twinningcage. The aforementioned arrangement is referred to as an "inside-out"machine. The wires to be twisted may also be supplied from outside thetwisting cage and taken up on a bobbin arranged within the bobbincradle. The latter configuration is sometimes referred to as "anoutside-in machine."

Outside-in machines are generally preferred in individual twistingmachines since the wire may be supplied from storage facilities ofsimple construction and greater capacity. In this case, the bobbincradle within the twisting cage is also required to hold only a singlebobbin. The outside-in machine is also readily adaptable for use with agreater number of wires.

If communication cables are made in one stage, the apparatus generallyemploys a plurality of twisting machines, or heads of the "inside-out"type.

The twisted elements so manufactured are directed to any type of take-up(e.g. stationary or rotating take-ups, single or double twist machines,capstan or extrusion lines) for laying up twisted wires to form acommunication cable. This is done in one operation.

The plurality of double twist twisting machines can be arrangedhorizontally or vertically, depending on the preferred plant layout.

One typical example of such an installation is disclosed in U.S. patentapplication Ser. No. 08/163,735 assigned to the assignee of the subjectapplication.

It is well-known in the art that the lay obtained with double twistactions is not perfectly regular and if longer lays are used, in orderto achieve higher speed of manufacture, some irregularity in theposition of the cores in the twisted elements have to be accepted.

These irregularities in the lays do not cause problems in communicationcables such as low frequency telephone cables used in standard telephoneapplications since the perfect constancy of the lays and in the relativeposition of the individual wires in each element (pair, triad or quad)are not that important.

With the advent of high speed data transmission, especially for computeruse and other applications, the frequencies required are much higher andtherefore standard pairs, triads or quads acceptable in telephonenetworks cannot be used in such high frequency applications.

In order to produce pairs, triads or quads that can operatesatisfactorily at these frequencies, it is necessary to produce a cablein which the elements of each pair, triad or quad are maintained in thesame desired position relative to each other so that the electricalcharacteristics of the pair, triad or quad do not vary along the lengthof the cable.

It is well-known, for example, that the characteristic impedance of ann-wire line is a function not only of the diameters of the individualconductors but also a function of the spacing or distances between theconductors. Matched impedances are critical at high frequencies tooptimize power transfer, reduce line reflections which causedeterioration of signal integrity and optimize the useful frequency forwhich the cable can be used.

It has been proven that for example, the characteristic impedance ofpairs can change drastically at different frequencies around itstheoretical average. Cables utilizing high quality pairs have beenproduced for use in communication local area networks with a maximumuseful frequency of 100 MHz. This, in the industry, is called a Level orCategory 5 cable. The specification for these cables requires, forexample, that the theoretical characteristic impedance of 100 Ohms canonly vary between 85 and 115 Ohms from Zero to 100 MHz.

This can only be achieved by assuring that the relative position of eachelement is maintained throughout the length of the cable. The acceptableway of achieving this has been to shorten the lays of the elements inorder to manufacture a mechanically more stable element. This approachhas naturally reduced the productivity of the equipment used since thereare physical limitations to the rotational speed of the bows used in thedouble twist machines.

The industry is already requiring twisted elements, especially pairs,that will maintain their electrical characteristics up to 350 MHz; thisis normally called a Level or Category 6 communication cable.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an apparatus formaking communication cables which does not have the disadvantages andlimitations inherent in comparable prior art machines.

It is another object of the present invention to provide an apparatus ofthe type aforementioned which is simple in construction in inexpensiveto manufacture.

It is another object of the present invention to provide an apparatus tomanufacture communication cable which can operate at significantlyhigher linear speeds than comparable machines currently being used formaking the same communication cable product.

It is a further object of the present invention to provide an apparatusfor making telephone cables which makes it possible to produce pairs,triads or quads with the same machines used in conjunction with theinvention covered in the aforementioned U.S. patent application Ser. No.08/163,735.

It is still an additional object of the invention to provide a methodfor efficient production of communication cable.

In order to achieve the above objectives and others which will becomeapparent hereafter, an apparatus for making communication cables inaccordance with the present invention comprises a frame and rotatingmeans for rotation around an axis relative to said frame. A cradle ismounted on said frame and determined and configurated to be containedwithin an envelope defined by said rotating means and adapted to receiveeither two reels, each one wound with single wires, or a single reelwound with a set of at least two separate or connected wires which canbe simultaneously unwound from the reel. It can also be adapted toreceive four reels which have been wound with single or connected wires.

Guide means guide the wires from said reel or reels on said stationarycradle to said rotating means and therefore to said stationary framethereby imparting at least one twist to the said at least two wiresunwound from the two reels or from one reel (wound with two separate orconnected wires).

Single and double twist machines can supply said twisting means topractice the invention.

On the same cradle a tape dispensing device is advantageously mounted sothat a tape with suitable dimensions and characteristics can be fedtogether with at least two wires coming from the reel or reels to theclosing point on the cradle. Therefore the tape and at least two wiresare twisted while the two wires and the tape pass through the rotatingmeans.

The method in accordance with the invention comprises the steps ofsimultaneously unwinding both a set of at least two wires wound on asfew as a single reel and a tape from the tape dispensing apparatus.

The wires and the tape are guided to a twisting station and impart atleast a single twist. In this manner a set of taped, twisted wires canbe produced. The same process can be used to unwind single wires from atleast two reels and the tape from the tape dispensing apparatus.

For more complex cables, the steps of the method are repeated in eachtwisting machine of a bank of twisting machines arranged in tandem toeach other. The method further comprises the step of taking up thetaped, twisted wires from all of the twisting machines at a pointdownstream from all such machines to form a composite cable.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, objects and advantages of the present invention willbecome apparent upon reading of the following detailed description ofthe preferred embodiment of the present invention when taken inconjunction with the drawings, as follows:

FIG. 1 is a diagrammatic front elevational view a machine line forproducing twisted pair cables in accordance with the present invention;

FIG. 1A is a cross-sectional view of the twisted and taped wire units orsets at CA in FIG. 1;

FIG. 2 is an enlarged front elevational view of the machine line shownin FIG. 1, illustrating in more detail the first two double twistingmachines of the bank of such machines arranged in tandem for twistingmultiple wires;

FIG. 3 is an enlarged cross-sectional view of the first double twistmachine shown in FIG. 2, taken along line 3--3;

FIG. 3A is an enlarged view of the machine shown in FIG. 3 illustratingthe details of the wire elements or conductors converging, being twistedand taped;

FIG. 4 is a top plan view of a modified twisting head arranged toaccommodate four separate reels or bobbins and a tape dispenser;

FIG. 5 is a front elevational view of the modified twisting head shownin FIG. 4;

FIG. 6 is a side elevational view of a section of a modified embodimentof an assembling means of the machine shown in FIG. 1, in which thetaping operations of the wire elements or conductors to form a compositecable are replaced by extruding operations; and

FIG. 7 is a side elevational view of the back end or downstream end ofthe machine shown in FIG. 6, showing extrusion-related operations andtake-up of the composite cable.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now specifically to the drawings, in which identical orsimilar parts are designated by the same reference numerals throughout,and first referring to FIG. 1, the apparatus for producing stabletwisted pair cables for high frequency use in accordance with thepresent invention is in the form of a machine line generally designatedby the reference numeral 10.

The machine 10 has an upstream end, on the left side of the machine asviewed in FIG. 1, where production of the cable commences and adownstream end, on the right side of the machine as viewed in FIG. 1,where the assembled or composite cable is taken up onto a take-up reel.The machine 10 will be described in the order of its sequencedoperations starting at the upstream end and moving towards thedownstream end.

At the upstream end, there is provided a housing or frame 12 whichhouses a plurality of twisting heads 14a-14d which form a bank oftwisting machines arranged in tandem along the longitudinal direction ofthe machine or line 10 as shown. Each of the heads 14a-14d is arrangedto produce an n-wire twisted set. For purposes of the description of thepreferred embodiments, each of the heads 14a-14d will be described asproducing twisted wire pairs. However, as will be more fully discussedbelow, the apparatus and method can equally be used to produce numerousother twisted wire combinations forming simple as well as complex cableconfigurations.

The first twisting head 14a includes bobbins 16a, 16b, each of which iswound with a single conductor or wire element, for reasons which will bemore fully discussed. The head 14a also includes a tape dispenser 16c.The twisting head 14a twists the two wire elements about each other andapplies the tape about the twisted wire elements to form a first twistedand taped pair C1 which is deflected 90° by roller or pulley 17 to movealong the longitudinal length direction of the machine 10 towards thedownstream end of the machine.

Similarly, the second twisting head 14b produces a similar twisted wirepair using wire elements or conductors from the bobbins 18a and 18bwhich are likewise twisted about each other and taped together with thetape from the dispenser 18c. A roller or pulley 19 deflects the secondtwisted wire pair 90° as shown so that it also now moves towards thedownstream end of the machine 10 substantially co-extensively with thefirst twisted wire pair C1, so that two twisted and taped wired pairsappear at C2. Similar operations are performed by the twisting heads 14cand 14d. Thus, a third twisted and taped wire pair is produced by thetwisting head 14c using the wire elements or conductors from the bobbins20a, 20b and tape dispenser 20c, the resulting twisted and taped wirepair being deflected by the pulley or roller 21 to present three twistedand taped wire pairs at C3 which move together towards the downstreamend substantially co-extensively with each other. Finally, the twistinghead 14d, using the wire elements or conductors from the bobbins 22a,22b and tape from the dispenser 22c produces a fourth twisted wire pairwhich, when deflected by roller or pulley 23, presents four twisted andtaped wire pairs at C4 all generally parallel to each other and movingtogether towards the downstream end. FIG. 1A is a cross-section of thewire units or sets at C4.

As will be more fully described in connection with FIG. 3, the bobbins16a, 16b, 18a, 18b, 20a, 20b, 22a and 22b are not themselves motorized.Accordingly, the four twisted and taped wire pairs at C4 are allsimultaneously drawn downstream by a belt capstan 24 which is providedwith a motive force, such as a motor drive 26. The specific capstan andmotor drive used are not critical for the purposes of the presentinvention, and any conventional or suitable components of this typeappropriate for the specific application may be used. In thisconnection, it may also be pointed out that the bobbins supported ineach of the twisting heads may themselves be motorized under certaincircumstances, particularly where the wire elements or conductors arethemselves relatively fragile and susceptible to excessive elongation orwhere friction plays an important factor in the overall forces orstresses developed in the individual conductors.

An optional measuring unit 27 is provided downstream from the beltcapstan 24 to provide a continuing indication of the linear speed ofmovement of the cable being produced by the twisting machines or heads.Here, a dancer 24' monitors the tension in the sets C4 and controls thetake-up speed of the composite cable at the downstream end of the line.

The four individual twisted and taped wire pairs are passed through aclosing die 28. Station 30, downstream from the closing die 28represents a pre-twister for pre-twisting the multiple wire sets inconjunction with the application of a tape to bind the multiple wiresets just prior to take-up on a rotating take-up to produce a cable witha continuous spiral or twist along the length of the cable. Where wirespecifications permit, it is also possible to periodically alternate thelays of the multiple wire sets, in which case the unit 30 may representan oscillator unit, the output of which can feed a composite cable intoan extruder, a cooling unit and a stationary take-up. However, thestation 30 may be omitted, in which case the continuously twisted setsform a composite cable taken up on the rotation take-up 32.Subsequently, such twisted cable can be inputted to an extruder to fixthe sets within the cable.

The last component or element shown at the downstream end of the machine10 is a common take-up 32 which includes a take-up reel or bobbin 34supported on a rotating cradle 36 which rotates about the axis A of themachine 10. A polar traverse 38 is preferably provided for distributingthe wire uniformly between the flanges of the bobbin 34. A suitabledrive is used to rotate the bobbin 34 about the axis A so as to providea twist to the composite cable C5 which enters the common take-up 32.The reference numeral 40 represents the position of the bobbin 34 in theloading/unloading positions before it is lifted to the cradle supportedposition.

Each of the twisting heads 14a-14d is driven so that at least onerotating element thereon, to be more fully discussed below, is rotatedto provide the necessary twists to the individual conductors or wireelements and the tapes. In FIG. 1, there is illustrated a drive shaft 42which is coupled to the drive 26, which also drives the belt capstan 24.The drive 26 includes a motor 26a, a motor pulley 26b, a driven pulley26c and a belt 26d engaging the two pulleys. The drive shaft 42 extendsupstream along the longitudinal direction of the machine 10 so as to beproximate to each of the twisting heads 14a-14d. Any suitable orconventional transmission arrangements can be used to transmit powerfrom the drive shaft 42 to the rotating elements of the rotating heads14a-14d.

Referring to FIG. 2, the specific transmission used in the describedembodiment is more fully illustrated. Thus, the shaft 42 is mounted insuitable bearings to rotate about a shaft axis A2. Mounted proximate toeach of the twisting heads there is provided a transmission fortransferring power and rotation to the twisting head. Since all of thetransmissions in connection with each of the four twisting heads 14a-14care the same, only the one transmission in connection with the twistinghead 14a will be described. A belt pulley or sheave 44 is mounted on thedrive shaft 42 for rotation about axis A2. As will be more evident fromFIG. 3, the twisting head 14a includes rotating elements which rotateabout a vertical shaft about axis A3 which is substantially normal tothe axis A2. A vertical rotating shaft of the twisting head 14a is fixedto a belt pulley or sheave 46 which is mounted for rotation about thevertical axis A3. A pair of deflecting pulleys, sheaves or rollers 48 ismounted on the stand or support structure 12a of housing 12 fordeflecting by 90° the direction of a flat belt 50 which is coupled tothe pulleys or sheaves 44, 46. Two deflecting pulleys or sheaves 48 needto be provided, as best shown in FIG. 3, for deflecting both portions ofthe belt which proceed towards the pulley 46 and return from the pulley46. It will be appreciated that the arrangement described provides aninexpensive and efficient method of driving each of the twisting heads.Other mechanical transmissions or individual motors for each head may beused, however, in order to drive the rotating elements of the twistingheads. In this connection, the drive shaft 42 may itself be formed oftwo or more sections of drive shaft coupled to each other by anysuitable means, such as a universal coupling 52 to transmit power to aplurality of twisting heads without the need to provide for a costlyinstallation which is highly sensitive to the critical positioning ofthe various coupled mechanical elements. This is particularly usefulwhen the machine 10 includes a large number of twisting heads all ofwhich are driven by a single drive shaft.

In selecting power transmissions for rotating the twisting heads14a-14d, provisions must be made for adjusting the gearing ratios sothat for a given rotational speed of the drive shaft 42, each of thetwisting heads 14a-14d can be rotated at slightly different speeds. Thisis particularly important in connection with high frequencycommunication cables in which cross-talk is to be minimized oreliminated. To do this, it is important to modify the lay lengths of thetwisted wire pairs, triads or quads so that the individual conductors ina given twisted set avoids being parallel to another wire or conductorin another twisted set. By changing the lay lengths of adjacent twistedsets, inter-wire coupling between different twisted sets and cross-talkis minimized. In the preferred embodiment, referring to FIG. 2, theadjustability of the lay for each individual twisting head can beadjusted by selecting the relative diameters of the pulleys 44 and 46,the ratio of the diameters of those two pulleys determining to whatdegree the twisting heads will rotate faster or slower than therotational speed of the drive shaft 42. Typically, traditional laylengths for twisted wire sets which have not been taped in accordancewith the present invention will vary within the range of 0.5-0.75inches.

Turning to FIG. 3, details of a twisting head 14a is illustrated ingreater detail. Generally, the twisting head is shown mounted forrotation about vertical axis A3 on a stand or support structure 12awhich forms a part of the housing 12. Because of the high speed ofrotation of the rotating elements forming part of the twisting heads,the twisting heads are normally and advantageously fully enclosed so asto prevent injury to personnel. Such enclosures are well-known andinclude a fixed cylindrical section 12b at the rear of the machine, asnormally viewed by an operator standing on the right side of the unit asviewed in FIG. 3. A second, pivotally mounted section 12c serves as aguard and can be moved so as to expose the twisting heads forreplacement of empty bobbins or tape pads as well as for servicing theunit.

The individual twisting heads 14a-14d are constructed very similarly totwisting heads described in U.S. patent application Ser. No. 08/163,735,assigned to the assignee of the instant application. Reference is madeto the aforementioned application, therefore, for at least some of thedetails of construction which will not be repeated here for the sake ofclarity and brevity. The discussion that follows will primarily focus onthe details of construction of the twisting heads which bear more fullyon the aspects of the present invention for the manufacture of uniformimpedance communication cables.

The stand or support structure 12a includes a horizontal table orsupport surface 12d on which there is fixedly mounted a verticalcylindrical support structure 12e as shown. Bearings 54, 56 are securedin the cylindrical support structure 12e as shown, these bearingsrotatably supporting a rotating shaft 58 which is substantially ofuniform external diameter with the exception of the central regionthereof, which is enlarged, as shown, for reasons to be described. Theupper end of the shaft 58 is similarly supported by bearings 60, 62which are housed within a vertical cylindrical structure 64 as shown.

The shaft 58 is connected or coupled to rotating bows 66, 68 which arediametrically opposed and connected at the lower ends thereof to arotating drum 70 which is itself connected to the vertical shaft 58 inany appropriate manner. In the preferred embodiment, such rotating drum70 is coupled to the vertical shaft 58 by means of horizontal webs,spokes, or walls 72a, 72b. For reasons which will be evident to thoseskilled in the art, and as well fully discussed in the applicant'searlier application Ser. No. 08/163,735, there is provided means 74(shown schematically in dashed outline) for fixing the position of areel cradle 76 against rotation about the axis A3 of the twisting head14a. In this way, while the bows 66, 68 can be rotated at extremely highspeeds, the elements now to be described, positioned within an envelope78 defined by the rotating bows 66, 68, remain stationary in relation tothe axis A3. One example of such cradle fixing means 74 is an epicyclictransmission which is coupled to the vertical cylindrical supportmembers 12e and 64. In this manner, the vertical cylindrical supportmember 64, which supports the cradle 76 itself becomes stationary inrelation to the axis A3 as is the cylindrical support member 12e.

The bows are arranged in a substantially balanced configuration forrotation about the axis A3 relative to the frame 12. While the specificsize or configuration of the bows 66, 68 is not critical, it will beevident that the dimensions as well as the shape of the bows 66, 68should be selected to provide a sufficiently large envelope 78 toaccommodate the various components or elements now to be described. Forthis reason, the transverse dimension along the horizontal directionbetween opposing peaks of the bows is shown to be greater than thespacing between the vertical ends of the bows along the axis A3. Suchconfiguration of the bows accommodates an arrangements of bobbins andtape dispenser as shown in FIGS. 1 and 2 wherein all of these componentsare mounted for rotation about axes substantially in a common horizontalplane. The configuration of the bows may need to be modifiedsignificantly if the bobbins and tape dispenser are mounted for rotationabout points which are offset from each other along the direction of theaxis A3. The specific arrangements of the bobbins and tape dispenser isnot critical for purposes of the present invention, and any sucharrangement may be used as long as the bows 66, 68 are suitablyconfigurated in order to generate an envelope 78 which will accommodatethe internal components of such inside-out machines and not come intocontact therewith.

The upper ends of the bows, as viewed in FIG. 3, are fixed to a rotatingsupport member 80, the lower portion of which is supported in bearings82 mounted on the upper arm or extent of the stationary reel cradle 76.

In the preferred embodiment being described, the reel cradle 76 supportstwo diametrically opposite reels or bobbins 16a, 16b which have beenwound with one or more wire elements or conductors. As commonlyunderstood in the art, a wire element or conductor is the metallic orconductive portion which is enclosed by an insulator coating or sheath.In FIG. 3, the bobbin 16b is rotatably mounted on spindle 84 which ismounted at one end thereof on the cradle 76. A wire element or conductor86 is diagrammatically shown as being unwound from the rotating reel 16babout axis of rotation A4 which is orthogonal to the axis A3 of rotationof the bows. The wire element or conductor 86 represents one or morewire elements or conductors, typically insulated, which may beseparately wound on the bobbin 16b or two or more wire elements orconductors which are joined or connected to each other along theirlengths and simultaneously payed off the bobbin as an integral elongatefilament. A deflection pulley 88 mounted on dancer arm 88' (FIG. 2)redirects the wire element or conductor 86 towards the axis A3 and intoan entry funnel 90 at the upper end of an axial bore 92 which extendsthrough the shaft 58. A similar deflection pulley cooperates with thewire element or conductor drawn off the bobbin or spool 16a, so thatboth wire elements or conductors are directed into the bore 92 throughthe entry funnel 90.

The first take-off pulley 88 is advantageously mounted on an arm 88' ofa dancer mechanism (not shown) which forms part of a constant tensionand brake device which cooperates with a brake disk 120 coupled to thereel 16b to control the braking forces applied to the reel 16b duringtake-off of wire therefrom. Such a tension adjustment and brakemechanism is of the type disclosed in U.S. Pat. No. 4,423,588, whereinit is more fully described.

An important feature of the present invention is the provision of a tapedispenser generally indicated by the reference numeral 94 arrangedwithin the envelope 78 for dispensing a suitable tape T. The tapedispenser 94 includes a support bracket 96 which is mounted on thecradle 76 and/or the vertical cylindrical support 64 to also render thebracket 96 stationary in relation to rotation about the axis A3. A tapepad 98 is mounted for rotation about an axis generally transverse to theaxis A3. Preferably a traverse wound tape pad is used in which theoverall tape length generally corresponds to the lengths of the wireelements or conductors wound on the bobbins or reels to minimize Thetape T is diagrammatically illustrated in FIG. 3 as being drawn off thetape pad 98, the reference numeral 100 indicating the orientation of thetape being drawn off when the tape pad is almost depleted, while thereference numeral 100' indicating the path of the tape when the tape padis full. In both cases, the tape T is guided about a roller 102 mountedon an upwardly projecting arm 104 as shown. The redirected tape T isdirected downwardly as shown for engagement with a dancer roller 106supported by an appropriate dancer 108 and thereafter redirected byrollers 110, 112 to a point along the axis A3 at which point the tape isredirected downwardly along the axis A3 and towards the entry funnel 90together with the conductors or wire elements drawn off from thebobbins. Preferably, there is provided some means upstream of the entryfunnel 90 (just above as viewed in FIG. 3) which assures that the tape Tis smoothly and uniformly applied to the incoming wire elements orconductors 86a, 86b. Such means may be in the form of a tape former tube113 fixedly mounted on the cradle 76 and having a bore 113a aligned withthe axis A3. The upper end 113b of the tube 113 preferably extends to aposition in proximity with the deflection roller 112 and is provided atthe lower end with a tapered conical surface 113c the smallest diameterof which substantially corresponds to the diameter of the bore 113a.With such a tube 113, the tape T, which is flat when it leaves thedeflection roller 112, is almost immediately brought into contact withthe tube 113 to thereby prevent the tape T from buckling or folding uponitself. The tape T is moved downwardly and spirally about the tube 113until it leaves the tapered conical surface 113c and is evenly appliedto the wire elements or conductors as they exit the tube as shown. Suchtape former tube 113 is commonly used to apply tape to avoid curling orfolding of the tape.

The wires and tape T are then directed towards a deflection pulley 114which is mounted on the enlarged mid-section of the rotating shaft 58 soas to provide a twist to the wire elements or conductors and twistingthe tape about such twisted conductors or wire elements to form asubstantially integral construction in which the spatial integrity ofthe twisted wires are maintained relative to each other. The twisted andtaped wire pair is then guided along the bow 66 in a conventional mannerfrom the lower end of the bows, as viewed in FIG. 3, to the upper endsthereof by suitable guides 116, such as eyelets, rollers or pulleyswhich are conventionally used for this purpose. Once the twisted andtaped wire pair reaches the upper end of the bows, another twist isimparted by means of an upper deviation pulley 118 which is rotatablymounted on rotating support member 80. The redirected twisted and tapedwire pair just past the upper deviation pulley 118 is represented by thedesignation C1 which is again deflected or redirected by deflectionpulley 17 mounted on the housing or frame 12 as previously indicated.

The specific tape T used is not critical and all tapes currently usedfor taping conductors may be used, as long as the tape is sufficientlyelastic to avoid breakage and excessive stresses and deformations of theconductor insulations. Since the tape only serves as a mechanicalbinder, a wide variety of tapes may be used, such as polyethylene tapessold as "Mylar." Other plastic and other foil tapes may be used.

The machine 10 can be used to provide uniform impedance communicationcables for high frequency use in numerous configurations and levels ofcomplexity. As suggested above, the presently preferred embodiment hasbeen described in connection with the formation of a composite cableconsisting of four twisted and taped wire pairs. Each wire pair isproduced on a separate twisting head 14a-14d, each twisting head havingbeen described as supporting two separate bobbins each of which suppliesa single wire element or conductor. However, in its broadest aspects,numerous modifications may be made both to the configuration of themachine as well as in its application. Thus, although a double twistarrangement has been shown in connection with each twisting heads14a-14d, it will be clear that single twist machines can also be used ateach of the twisting stations or in combination with double twistingmachines. The extent of twisting, in that event, will, of course, bedifferent and the productivity of the overall machine may be somewhatcompromised because of the lower operational speeds of single twistmachines. Furthermore, while the bank or arrangement of the twistingmachines has been described as including four twisting heads, it shouldbe clear that a single twisting head may be utilized for the productionof the simplest twisted wire pair conductors or numerous twisting unitsmay be used, one for each twisted wire configuration to be included in acomposite cable. Furthermore, as suggested, in the production of thesimplest twisted pairs, each of the bobbins may issue a single wireelement or conductor. However, other numerous approaches can be taken.It is only important, in fact, that the cradle 76 be dimensioned toreceive as few as a single reel wound with a total of at least twoseparate or connected wires which are simultaneously unwound therefrom.Thus, it is possible to include but a single reel on which there havebeen wound two separate wire elements or conductors which aresimultaneously unwound. However, it is possible to use integrally formedinsulated wire elements or conductors which have been joined along theirlengths, such as by connecting webs between the respective insulationsor by joining the insulations directly to each other as by fusion oradhesive. Numerous combinations or permutations can clearly beenvisioned. Thus, if a twisted wire triad is to be formed, this can beachieved with either three bobbins each issuing one single wire elementor conductor, two reels one of which issues a single wire element orconductor and the other issues two separate or connected wire elementsor conductors, or even a single reel which issues three wire separate orconnected elements or conductors. The formation of a twisted wire quadcan likewise be formed in a number of different ways, such as twoseparate or connected wires issuing from each of two reels, two reelsone of which issues a single wire element or conductor and the otherissues three separate or connected wire elements or conductors, or fourreels each issuing a single conductor. The latter configuration is,indeed, illustrated in FIGS. 5 and 6, in which two bobbins are eachmounted on a common shaft and each bobbin issues a single wire elementor conductor, in which case the four wire elements or conductorstogether with the tape are guided towards the axis of the twisting head,and in particular, the axis of the rotation of the bows so that the fourwire elements or conductors are twisted about each other andsimultaneously taped to fix or maintain the spatial integrity of all ofthe twisted wires relative to each other. Such a twisted wire quad can,in turn, be combined with other twisted wire configurations to form amore complex composite cable. The drawing off of a plurality of wireelements or conductors from a single bobbin and twisting such wiresabout each other, although without the taping of these wires, isdisclosed in the aforementioned U.S. patent application Ser. No.08/163,735.

It will be appreciated, therefore, that the method of producing uniformimpedance communication cables for high frequency use comprises thesteps of simultaneously unwinding a total of at least two wires from asfew as a single reel. Tape is dispensed and guided along with the wiresto a twisting station at which the wires are twisted about each otherwith a predetermined lay and the tape is wound about the twisted wiresto fix or maintain the spatial integrity of the twisted wires relativeto each other. In this manner, the desired electrical properties of thetwisted wires are assured and maintained constant. The individuallytwisted and taped wire sets, exhibiting different lay lengths, can thenbe combined and further twisted about each other to form a compositecable. As indicated above, such twisting of the wires about each othercan be performed by imparting a single twist or a double twist to suchwires and tape. This method can be used to produce high quality uniformimpedance communication cables for high frequency use made up of aplurality of n-wire twisted sets, where n can be equal to 2, 3, 4 or anyother desired number as practiced within the trade.

In the embodiment illustrated in FIG. 1, the twisted and taped wirepairs at C4 are taped together to bind the multiple wire sets just priorto take up to form a composite cable with a continuous spiral or twistalong the length of the cable. As previously indicated, however, theunit 30 may be replaced with an oscillator unit to periodicallyalternate the lays of the multiple wire sets, and the output can be fedto an extruder unit. Such an arrangement is illustrated in FIGS. 6 and7.

FIGS. 6 and 7 illustrate the intermediate and downstream ends of amodified line which replace a number of elements or components shown inFIG. 1 downstream of the belt capstan 24. Thus, in FIGS. 6 and 7, theoscillator 130 periodically reverses the lays of the multiple wire setsC4 and imparts sufficient twists of the individual wire pairs to provideadequate stability to the twisted pairs to at least temporarily maintainthe physical integrity of the composite cable until the composite cableis passed through an extruder. However, an optional binder unit 132 maybe provided just downstream of the oscillator 130 to apply any wellknown binder material to the composite cable to enhance its stabilityand retain the wire sets in their desired relative positions ororientations. Downstream from the oscillator 130, and the binderapplication unit 132, if one is used, there is provided conventionalextruder 134 in which an external protective sleeve or sheath (FIG. 1A)is applied to fix the relative positions and orientations of the wirepairs. The composite cable can now be processed in accordance withwell-known techniques, including passing the extruded composite cablethrough a cooling unit 136, a capstan and cooling box 138, and a vacuumwiper 140 from which the composite cable can be taken up on dualtake-ups 142. It will be appreciated, therefore, that the formation ofthe wire pairs in both embodiments is the same. The only differencebetween the two embodiments is the manner in which the individual wirepairs are permanently secured to each other to form a composite cable.In the embodiment of FIG. 1, a tape is externally applied to theplurality of wire pairs, while in FIG. 6 a sheath or sleeve is extrudedexteriorally of the wire pairs. In both cases, a mechanical method isused to secure the wire pairs to each other in fixed relative positionsto each other.

Since the characteristic impedance of an n-wire twisted line ofindividual wire elements is a function of the diameters of theindividual conductors, the spacing therebetween and the electricalproperties of the material occupying the space between the conductors(e.g. air or insulation), it is important in the production of suchuniform impedance communication cables suitable for high frequency usethat when twisting insulated conductors about each other, the diametersof the wire elements as well as the diameters of the insulation beselected and maintained within close tolerances so as to avoid anymeaningful deviations in those geometrical parameters. Additionally,eccentricity of the electrical wire conductors as positioned within theelectric insulation should be minimized, typically less than 90%. Oncethe eccentricity as well as the geometrical dimensions of the insulatedconductors can be closely monitored, it is also desirable that theapplication of the tape about the twisted conductors be at asubstantially uniform pressure so as not to produce different levels ofdeformation of the insulating layers since this would, in effect, modifythe spatial relationships and spacings between the conductors. Changesin the compression or deformation of the insulating layers would,accordingly, change the characteristic impedance along the length of theconductors and this would produce unpredictable and undesirable changesin electrical characteristics or properties which, particularly athigher data transmission rates and higher frequencies, could adverselyaffect the impedance of the cable, power transfer and upper frequencylimits at which the cable is useful.

Twisted wire lines of the type above discussed are becoming increasinglyimportant as efforts are made to increase rates of data transfer inconnection with computer networks, sophisticated telephone services andbroadcast of audio and video programming. In order to meet this demand,the cables made in accordance with the present invention providepredictable and stable electrical characteristics at frequencies inexcess of 300 mHz, significantly higher than the frequency range ofcables that are currently used and classified as Level 5 by EIA/TIAstandards. By physically securing the twisted conductors to each other,by taping, and, in effect, locking them to each other, their spatialrelationship becomes fixed, notwithstanding any bending of the resultingcable. Such fixing of the spatial relationship sets and maintains thecharacteristic impedance of the cable at a desired level which minimizesreturn losses, and impedance imbalances. As a result of such more evenimpedance, significant improvements in signal integrity can be achieved.Such control of conductor-to-conductor spacing and tension, whichachieves more predictable and uniform impedance along the length of theconductors is achieved with a technique which allows for high productionrates and minimum construction costs. With this invention one canachieve the same desirable electrical characteristics with larger laylengths thereby increasing productivity of the cable withoutcompromising its electrical properties.

The invention has been shown and described by way of a presentlypreferred embodiment, and many variations and modifications may be madetherein without departing from the spirit of the invention. Theinvention, therefore, is not to be limited to any specified form orembodiment, except insofar as such limitations are expressly said forthin the claims.

I claim:
 1. Apparatus for the manufacture of uniform impedancecommunication cables for high frequency use comprising a frame; rotatingmeans arranged in a substantial balanced configuration for rotationabout an axis relative to said frame, said rotating means including arotating element offset from said axis which defines an envelope as saidrotating element rotates about said axis; a cradle dimensioned toreceive as few as a single reel mounted within said cradle, said as fewas a single reel being wound with a total of at least two wires whichare simultaneously unwound from said as few as a single reel; cradlefixing means for maintaining the position of said cradle substantiallyfixed about said axis relative to said frame during rotation of saidrotating means; tape dispensing means arranged within said envelope fordispensing tape; and guide means for guiding said at least two wires andtape to said rotating means for twisting the wires about each other witha predetermined lay and winding the tape about the twisted wires to fixand maintain the spatial integrity of the twisted wires relative to eachother, wherein a plurality of like apparatus are provided each includingsaid rotating means; and further comprising take up means for receivingand winding a plurality of sets of double twisted wires generated byeach of said apparatus, assembling means for assembling said pluralityof sets of double twisted wires, said assembling means comprising meansfor applying tape about said plurality of sets of double twisted wiresto form a composite cable, whereby desired electrical properties of thetwisted wires is assured.
 2. Apparatus for the manufacture of uniformimpedance communication cables for high frequency use comprising aframe; rotating means arranged in a substantial balanced configurationfor rotation about an axis relative to said frame, said rotating meansincluding a rotating element offset from said axis which defines anenvelope as said rotating element rotates about said axis; a cradledimensioned to receive as few as a single reel mounted within saidcradle, said as few as a single reel being wound with a total of atleast two wires which are simultaneously unwound from said as few as asingle reel; cradle fixing means for maintaining the position of saidcradle substantially fixed about said axis relative to said frame duringrotation of said rotating means; tape dispensing means arranged withinsaid envelope for dispensing tape; and guide means for guiding said atleast two wires and tape to said rotating means for twisting the wiresabout each other with a predetermined lay and winding the tape about thetwisted wires to fix and maintain the spatial integrity of the twistedwires relative to each other, wherein a plurality of like apparatus areprovided each including said rotating means; and further comprising takeup means for receiving and winding a plurality of sets of double twistedwires generated by each of said apparatus, assembling means forassembling said plurality of sets of double twisted wires, saidassembling means comprising means for extruding a sheath about saidplurality of sets of double twisted wires to form a composite cable,whereby desired electrical properties of the twisted wires is assured.